The instrument work on the basic principle of Beers-Lamberts Law, it states that the amount of absorption is directly proportional to the concentration of elements.
The technique uses basically the principle that, free atoms generated in an atomizer can absorb the radiation at specific frequency.
Atomic absorption spectroscopy quantifies absorption of ground state atoms in the gaseous state.
The atoms absorb UV or Visible light and make transition to high electronic energy levels. The analyte concentration can be determined from the amount of absorption.